1. Field of the Invention
The present invention relates to an apparatus and method for preventing performance degradation of a call service in a portable terminal. More particularly, the present invention relates to an apparatus and method for preventing performance degradation of a call service in a portable terminal, which is caused when the portable terminal does not perform an acquisition process with a system that it has failed to access, for a predetermined time in a weak electrical field.
2. Description of the Related Art
In general, a portable terminal acquires a system in its current region. If the acquired system is not listed as the most preferred system in a Preferred Roaming List (PRL), the portable terminal may perform system reselection every 3 minutes in order to acquire the most preferred system.
However, power is consumed during the reselection for acquisition of the most preferred system every 3 minutes. To conserve power, the selection process to acquire the most preferred system with which an access attempt has failed is discontinued for 15 minutes, when Max Access Probe Exit (MAPE) occurs during the reselection.
If the portable terminal does not receive a paging channel response from a base station despite a plurality of (1+NUM_STEP, up to 16) access probe transmissions, the portable terminal repeats the same process at a predetermined time (RS+RD) later. A sequence of access probes is referred to as an access sequence. If the portable terminal fails to receive a paging channel response from the base station despite transmitting the access sequence MAX_REQ_SEQ (up to 15) times, this is considered an access attempt failure and thus MAPE occurs.
However, when a predetermined number or more failures of call origination and termination bring about MAPE in a weak electrical field region where one system exists, the portable terminal does not perform a selection process, used to acquire the most preferred system with which the access attempt has failed, for 15 minutes in order to conserve power.
Accordingly, even though the portable terminal moves from the weak electrical field region to a strong electrical field region and thus is capable of acquiring the most preferred system, it can neither originate nor terminate a call for 15 minutes. This long unavailability of the call service degrades the performance of the call service.